I think this will come largely down to DM's discretion. I had a somewhat similar situation where we were fighting in a room which had a side entrance just waiting to be used as an ambush vector. One guy dumped some lantern oil in the square next to the door. When the ambusher came, he slipped one square and fell prone. I (playing a telekenetic psion) moved the enemy back into the square with the oil, and then brought a lit log from the fireplace on the other side of the room to ignite the oil. I don't remember how much damage the enemy took, but it was fun.
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IsziFeb 27 '12 at 5:49

3 Answers
3

If it is normal fire. I would make the fire do 5 fire damage per tier if a character starts its turn or moves through a square affected by the fire. This seems in line with the DMG's traps and other hazards that involve fire.

If it is magic fire (a zone from a spell, or some other kind of thing) I would just expand the zone of the spell and use its effects.

I think these kind of fuzziness comes from the relatively new design paradigm that adds flavorful powers to player's list of options.

I think no clear rule could be directly inferred from the rules (I was unable to find how). As a DM, I'd change the effect of Control Flame to (emphasis on suggested editing):

[...]
Expand: The fire expands to an unoccupied square adjacent to it.
Extinguish: The fire is extinguished.
Relocate: You slide the fire up to 2 squares.
[...]

After all, it is an Utility power (not an attack one).

In this way it shouldn't be possible to attack a creature using this power. If you stop sustaining it after having relocated a flame, the flame itself returns to its original square. If the original square happens to be occupied, then the creature could take some fire damage. However, the timing at which the creature takes damage (immediately, at the start of its turn?) and the amount of damage it takes should be determined by the DM as part of the encounter specifics (fire squares are usually hindering terrain).

This is really a comment, not an answer to the question. Please use "add comment" to leave feedback for the author.
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wax eagleAug 14 '12 at 13:15

As an answer, this seems incomplete. Would you use the improvised weapon rules out of the box, or add fire keywords? Use strength for attack and damage using a melee basic with an improvised weapon?
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Simon WithersAug 21 '12 at 0:17